Actually SPEC is the lightest flywheel available.
It weighs in at 7.97lbs on a digital scale and also comes balanced to the disc and pressure plate if you order the whole package.
Also 20lbs (SVT) and 22lbs (stock) are both light for stock flywheels.
Like stated most OEM's are in the 30lb range with several weighing up to 50lbs. (especially when you get into that dual mass BS)
